Acute rhinosinusitis is one of the most common reasons for physician visits and is associated with significant morbidity, lost time from work, and treatment costs. In primary care, the vast majority of patients presenting with acute rhinosinusitis-like complaints suffer from viral infections. Although bacterial superinfection or complications from bacterial infection are relatively rare;treatment is almost always with an antibiotic, because no easy to use test to distinguish bacterial from self limiting viral infection exists. Antibiotics, however, provide little clinical benefit due to the high rate of spontaneous improvement. There appears to be a subset of patients that may benefit from an antibiotic, but no clinical factors or feasible diagnostic tests have been identified to help primary care physicians to identify these patients, and no effective, alternative, treatments have been identified. Consequently, antibiotics are over prescribed. Recently, two potential alternative symptomatic therapies have been identified - corticosteroids and saline nasal irrigation (SNI). Although intranasal corticosteroids have been shown not to be effective, early studies suggest that a short course of oral steroids may have a beneficial effect. In chronic sinusitis, positive gravity based SNI with a nasal irrigation cup improves symptoms and quality of life (QOL), and many patients have embraced the use of these devices. Potentially, the effect of SNI could be additive to the effect of either antibiotics or oral steroids. Our goal is to assess the overall effectiveness of antibiotics, identify prognostic indicators for benefit from antibiotic treatment, and assess the effectiveness of a short course of oral steroids and of SNI in adults with clinically diagnosed acute rhinosinusitis. We will randomize 928 eligible adults from 3 centers in the United States and 6 centers in Europe. Using a factorial design, subjects will be randomized to receive one of 8 different treatment options: 1) antibiotic with placebo steroid;2) steroid with placebo antibiotic;3) antibiotic with steroid;4) placebo antibiotic and placebo steroid. Half of each of these groups will receive SNI and the other half control irrigation. In addition, all subjects will receive an analgesic and possibly other symptomatic treatments. The primary outcome is the disease-specific QOL at Day 5 measured with the SNOT-16, a validated evaluative instrument. We will also assess duration of illness, treatment failure, reconsultation, missed work, satisfaction with treatment and adverse events. Subject outcomes will also be assessed by daily symptom diary and telephone interviews at days 5, 10, 28 and 180. We hope to translate the results of this study into improved primary care, more judicious usage of antibiotics, and enhanced QOL for patients.